The Impact of the 1936 Corn-Belt Drought on American ... · Page 1 of 42 Draft of December 8, 2009...

Sutch: The Impact of the 1936 Corn-Belt Drought

of 42 Draft of December 8, 2009

The Impact of the 1936 Corn-Belt Drought on

American Farmers’ Adoption of Hybrid Corn

Richard Sutch

University of California, Riverside

and the

National Bureau of Economic Research

Draft of January 6, 2010

ABSTRACT

The severe drought in 1936 revealed an advantage of hybrid corn not previously

recognized – its drought tolerance. This revealed ecological resilience motivated some

farmers to adopt hybrids despite their commercial unattractiveness in normal years. That

response to climate change had a tipping effect. The increase in sales of hybrid seed in

1937 and 1938 financed research at private seed companies that led to new varieties with

significantly improved yields in normal years. This development provided the economic

incentive for late adopters to follow suit. Because post-1936 hybrid varieties conferred

advantages beyond improved drought resistance, the negative ecological impact of the

devastating 1936 drought had the surprising, but beneficial, consequence of moving more

farmers to superior corn seed selection.

Thanks to Vilma Helena Sielawa Ferreira, Connie Chow, and Hiroko Inoue for research assistance, to

Susan B. Carter for critical advice, and to Norman Ellstrand for assistance with the plant biology.

Comments by Paul David, Bronwyn Hall, Gary Libecap, Michael Roberts, Paul Rhode, Hugh Rockoff,

Richard Steckel, and Gavin Wright on earlier drafts are gratefully acknowledged. Parts of this chapter

were previously released as a National Bureau of Economic Research Working Paper Number 14141

[Sutch 2008]. Financial support was provided by a National Science Foundation Grant: ―Biocomplexity in

the Environment, Dynamics of Coupled Natural and Human Systems.‖ Administrative support was

provided by the Biotechnology Impacts Center and the Center for Economic and Social Policy at the

University of California, Riverside.



A severe and sustained drought struck central North America during the 1930s. Centered

on eastern Kansas, it extended north into the Canadian prairies, east to the Illinois-

Indiana boarder, south to the Gulf of Mexico, and west into Montana and Idaho. See

Figure 1. The seven-year period of low rainfall and high temperatures, 1932-1938, was

unprecedented in the memory of the Euro-Americans who inhabited the region in its

extent, severity, and duration. It has been described by climate scientists as ―one of the

most severe environmental catastrophes in U.S. history‖ [Schubert et al, 2004: 1855].

The period is best remembered for the ―Dust Bowl‖ conditions created on the panhandles

of Texas and Oklahoma, and adjacent parts of New Mexico, Colorado, and Kansas.1

My interest in this paper is – not with the Dust Bowl – but with the Corn Belt that

lies to the northeast of the Dust Bowl. Figure 1 also displays the outline of the Corn Belt

on the drought map. As can be seen, the eastern portion of the Corn Belt (western Ohio,

and Indiana) was largely outside the region struck by the severe drought. By contrast the

western Corn Belt (southwest Minnesota, western Iowa, southeast South Dakota, and

eastern Nebraska) was hard hit. This geographical contrast will allow me to explore the

adaptations made by corn farmers to sudden climate change. The lens through which I

will look is the adoption of hybrid corn in the 1930s.

The suggestion that I make in this chapter is that the severe drought of 1936

revealed an advantage of hybrid corn not previously recognized – its drought tolerance.

This ecological resilience motivated some farmers to adopt hybrids despite their

commercial unattractiveness in normal years. But that response to climate change had a

tipping effect. The increase in sales of hybrid seed in 1937 and 1938 financed research at

1 The Dust Bowl is not synonymous with the drought area. The Dust Bowl had a naturally semi-arid

climate and was settled during an untypical period of favorable climatic conditions. The first farmers

imposed a ―system of agriculture to which the Plains are not adapted to bring into a semi arid region

methods which, on the whole, are suitable only for a humid region.‖ Arid conditions returned with the

North American precipitation anomaly of the 1930s. For more detail see the Report of the President’s

Great Plains Drought Area Committee [August 27, 1936], Libecap and Hansen [2004], and Hornbeck

[2009].



private seed companies that led to new varieties with significantly improved yields in

normal years. This development provided the economic incentive for late adopters to

follow suit. Because post-1936 hybrid varieties conferred advantages beyond improved

drought resistance, the negative ecological impact of the devastating 1936 drought had

the surprising, but beneficial, consequence of moving more farmers to superior corn seed

selection sooner than they might otherwise.

There is no doubt that the drought decimated corn crops in 1934 and 1936. One

index of the impact is the fraction harvested of each year’s acreage planted to corn.

When the damage to the crop is extensive, it is not worthwhile to attempt a harvest. If the

damage is total, there is no crop to harvest. Figure 2 presents the percentage of the corn

acreage planted that was harvested in the state of Iowa for the years 1926 to 1950. The

two years 1934 and 1936 stand out as quite depressed. Figure 3 displays the data for

Illinois (top panel), a state that was less affected by the participation shortfall, and Kansas

(bottom panel), a hard hit state at the epicenter of the drought.

Another index of drought is the yield (in bushels of corn per harvested acre).

Figures 2 and 3 also display the yield statistics.2 As Figure 3 suggests, the yield data is

somewhat less satisfactory as an index. All we have for most counties and crop districts

is the yield per harvested, not planted, acres. In a state like Kansas only a very small

fraction of the acreage was harvested, presumably located in areas that escaped the worst

of the drought. On those privileged farms relative yields were depressed but not to the

extent in percentage terms as in Iowa. In a state like Illinois the drought effect is more

evident in the harvest-to-planting ratio than in the yield per harvested acre.

The Adoption of Hybrid Corn

Hybrid corn (technically ―double-cross inbred-hybrid corn‖) was ―invented‖ by Donald

2 Unpublished state and county level data on acreage planted and harvested was made available by Michael

Haines. I am most grateful.



F. Jones in 1917-1918 and was developed and introduced on a trial basis in 1924 by

Henry Agard Wallace. In the 1920s the Iowa Experiment Station began scientific field

trials. Wallace’s hybrid was first entered in the Iowa tests in 1921. It won first place in

1924. It was first sold commercially in 1925. Competitors began sales in 1928.

Widespread commercial adoption began in 1932 [Olmstead 2006: IV-9; Zuber and

Robinson 1941: 589]. The US Department of Agriculture began tracking the adoption of

the new varieties in the following year, 1933. At that time only about 0.1 percent of the

nation’s corn acreage was planted to the new seed. In 1936 the USDA proclaimed

significant increases in yield per acre could be achieved by adopting hybrid corn [Jenkins

1936: 481]. Yet it took another decade before 70 percent of the corn acreage had been

planted with hybrid seed. By 1960, 96.3 percent of acreage was planted to hybrid

varieties [USDA, Agricultural Statistics 1962, Table 46: 41; USDA, Track Records,

April 2004: 19]. Figure 4 reproduces the annual data for the country as a whole and

reveals a lazy S-shaped cumulative diffusion pattern.3

Zvi Griliches made the adoption of hybrid varieties in the United States the

exemplar for a statistical model of technological diffusion and fitted the cumulative

adoption patterns reported by the USDA to a logistic curve [Griliches 1957b]. Despite the

nearly three decades between initial adoption and full acceptance, Griliches considered

the adoption pattern displayed in Figure 4 to have been remarkably rapid [p. 502]. By

examining the pattern of adoption, first, state by state, and then, crop district by district,

he argued that at the local level adoption proceeded rapidly. But, he continued, the initial

introduction into a local farming community proceeded slowly as commercial seed

3 National and state level data on the percentage of corn acres planted to hybrids are available in various

annual issues of Agricultural Statistics. I have relied on the volumes for 1945 (Table 46, p. 42), 1948

(Table 50, p. 48), 1950 (Table 49, p. 47), 1952 (Table 43, p. 40), 1954 (Table 38, p. 30), 1957 (Table 40, p.

39), 1959 (Table 43, p. 33), and 1961 (Table 43, p.33). The year 1960 is the last date this data is available.



producers developed and marketed acceptable hybrids in different locales. Thus the rate

of diffusion across the US proceeded slowly [p. 507].

Griliches’s explanation for the rapid and complete abandonment of open-

pollinated corn in favor of the new hybrid varieties was based on a simple set of ―stylized

facts.‖ He considered hybrid corn superior to the traditional open-pollinated varieties

from the beginning and suggested that that superiority was established in 1935 and

persisted thereafter.4 The advantage of hybrids, according to Griliches, could be

objectively measured by the relative increase in yield over the open-pollinated corn

[Griliches 1957b: 516-517]. He assumed that the new varieties required no significant

increase in capital investment or annual inputs. According to this analysis the adoption

process in a given crop district was one of disequilibrium transition [p. 503]. Griliches

attributed the lags in the process to ―imperfect knowledge.‖ It ―takes time to realize that

things have in fact changed‖ [p. 516]. The spread of hybrid corn geographically was

slowed by the supply lags in developing and introducing hybrid varieties tailored to the

specific soil type, weather conditions, and latitude of the peripheral regions.5 But even

this process was rapid. Using the rule of thumb suggested by Griliches to mark the start

of an adoption process as the date that ten percent of acreage was planted to hybrid corn,

Iowa in 1936 was followed by Illinois, Indiana, and Wisconsin in 1937, by Minnesota in

1938, and by Ohio, Nebraska, and Missouri in 1939.

4 The date 1935 is the year that acreage planted to hybrid corn exceeded ten percent of the total in the

district at the heart of the hybrid revolution. Griliches chose ten percent ―as an indicator that the

development had passed the experimental stage and that superior hybrids were available to farmers in

commercial quantities.‖ The region where this breakthrough occurred was the Sixth Iowa Crop Reporting

District [Griliches 1957b: 507 and Table II, p. 508]. The sixth district comprised Bremer, Black Hawk,

Benton, Buchanan, Linn, Delaware, Jones, Dubuque, Jackson, and Clinton Counties, all in Iowa.

5 Paul David, in an insightful review, has criticized the Griliches approach ―for lacking any real micro-level

technology choice model‖ [David 2006:4]. Edwin Mansfield [1961] can be credited with supplying such a

model to explain the logistic shape (although as David points out, Mansfield’s model is simply one of many

formulations consistent with the data). Mansfield suggested that the probability that a non-user would

switch to a new technology would be a function of the number of those in the immediate neighborhood

who had already accepted the technology. This ―contagion‖ model, borrowed from epidemiology, leads to

the logistic diffusion curve. Bronwyn Hall [2004] provides a review of the theoretical literature on

diffusion from both sociology and economics.



The development of hybrid corn and its rapid adoption were, nearly from the

beginning, hailed as a triumph of twentieth-century biotechnology and one that carried

with it enormous welfare benefits [Sprague 1946:101].6 In a chart that is perhaps even

more famous, at least among plant scientists, than Griliches’s logistic, the rise in corn

yields per acre is employed to suggest that hybrid corn was responsible for a

biotechnological revolution that abruptly ended a sustained period of ―biological stasis.‖

Figure 5 displays the ―hockey stick‖ graph reproduced dozens of time in the scientific

literature.7 The chart plots USDA statistics on corn yields per acre dating back to 1866.

There was a remarkable stability in yields with no discernable trend before 1936.8

Thereafter yields began to increase and they have continued upward ever since. Yields

per acre rose from an average of 25 bushels per acre before 1936 to 135 bushels per acre

in the years 2000-2002 [Carter et al 2006: Series Da693-694], more than a five-fold

increase. Perhaps too casually, this increase has been attributed (1) to the continuing

adoption of the hybrid varieties between 1936 and 1960 and (2) to the continuing

improvement of hybrid traits as new varieties were introduced between 1936 and 1989

[Duvick 1992].

I say ―perhaps too casually,‖ because the introduction of hybrids was also

accompanied by the increased use of synthetic nitrogen fertilizers, increased planting

densities, and the adoption and improvements in planting and harvesting machinery.

However, these developments were intimately interrelated. One of the hybrid traits

introduced improved the plant’s ability to absorb nitrogen fertilizers and indeed the use of

6 Griliches estimated the rate of return on hybrid corn research to have been at least 700 percent annually as

of 1955 [Griliches 1958: 419].

7 As an indication of how ubiquitously Figure 5 appears, I note that a standard textbook on corn for plant

scientists [Smith, Betrán, and Runge 2004] reproduces a version of this chart four times in four separate

chapters [Troyer 2004: Chapter 1.4, Figure 32, p. 218; Betrán, Bänziger, and Menz 2004: Chapter 2.3,

Figure 6, p. 351; Wisner and Baldwin 2004: Chapter 3.8, Figure 2, p. 759; and Halauer 2004: Chapter 4.4,

Figure 1, p. 901].

8 Alan Olmstead and Paul Rhode have challenged the notion of a biological stasis before 1936. They view

the stability of yields before 1936 as due to a balance of conflicting forces some of which would depress

yields and counterbalancing ones that worked to raise yields [Olmstead and Rhode 2008: 64-97].



fertilizer was required to reach the potential of the hybrids. Similarly, the increased

planting densities were possible only because of traits that reduced the plant’s

requirements for full sunlight and that increased its resistance to lodging – the tendency

of the plant to lie down or fall over when beaten down by the wind. Even then high

density was possible only with the heavy application of fertilizer. Increased planting

densities also required the abandonment of the horse and the horse-wide path between the

rows of corn. Thus the adoption of machinery was a necessary component for achieving

the full potential of hybrid corn.9 Since hybrid seed, synthetic fertilizer, and gasoline

tractors were a necessary triad, it is not really possible to partition responsibility for the

yield increases among them.10

The continuing improvement in the performance of hybrids after their initial

introduction is an important part of the story. Figure 6 reproduces the results of field

experiments conducted in 1989 and 1990 in central Iowa. Forty-one varieties introduced

between 1934 through 1989 by Pioneer Hi-Bred (a leading seed producer and a key

player in the story to follow), ―all popular in their time,‖ together with the most famous

open-pollinated variety, Reid’s Yellow Dent, were planted in adjacent fields in a

demonstration designed to illustrate the advance of yields due to genetic improvement

[Duvick 1992: 70]. As Figure 6 illustrates, yields advanced at an average rate of 1.16

bushels per acre per year throughout this 55-year period.11

9 On these points see: Castleberry, Crum, and Krull [1984: 33]; Shaw and Durst [1965, Table 21, p. 39];

Johnson [1960], and Sutch [2008].

10 The biological revolution in corn, commonly associated with the introduction of hybrid varieties, was not

a unique phenomenon. Indeed, I find remarkably similar ―hockey stick graphs‖ for the yields per acre in

cotton, wheat, tobacco, oats, potatoes, and barley [Sutch 2008: 19-26] . The simultaneous increase in the

yields of so many different crops during this period is more properly attributed to the discovery of an

economical process for synthesizing ammonia and the consequent increase in the use of synthetic fertilizers

[Smil 2001].

11 Also see Cardwell [1982], Russell [1983] and Castleberry, Crum, and Krull [1984].



Despite the undeniable improvement in plant traits and the obvious appeal of the

Griliches adoption story, I make the following claims:

1] There was not an unambiguous economic advantage of hybrid corn over the

open-pollinated varieties at the time of planting in 1936.

2] The early adoption of hybrid corn before 1937 can be better explained by a

sustained propaganda campaign conducted by the U.S. Department of Agriculture at the

direction of the Secretary of Agriculture, Henry Agard Wallace. The Department’s

message echoed that of the commercial seed companies. Wallace was the founder of the

Pioneer Hi-Bred Seed Company, the first and largest producer of hybrid seed.

3] Later adopters of hybrid seed were motivated by the drought resistance of one

experimental hybrid variety vividly demonstrated during the drought of 1936. The

eventual improvement of yields as newer varieties were introduced and the imitative

force of ―collective logic‖ explain the continuation and acceleration of the process.

Given the required capital investments in fertilizer tanks and tractors and the inability to

save and plant one’s own seed, adoption tended to be irreversible.

The Iowa Corn Yield Tests and Hybrid Superiority

Griliches assumed that hybrid corn had an economically significant and unambiguous

superiority over open-pollinated corn from the time it was first introduced. He reported

that this superiority could be gauged by a 15- to 20-percent higher yield achieved with

hybrid corn over the traditional open-pollinated varieties. Griliches also suggested that

this relative advantage applied to both high- and low-yielding soils, good years and bad

[Griliches 1957b: 516-517; 1958: 421]. His citations to support this estimate of the yield

advantage were from an unpublished Federal Commodity Insurance Corporation source

dated 1942, and published sources dated 1940 [USDA], 1946 [Sprague], and 1952

[Rogers and Collier]. None of these sources referred to the 1932-1936 period of early

adoption. The 1940 USDA report cited the claims of ―plant breeders‖ [Griliches



1957b:517].12

G.F. Sprague, an agronomist at Iowa State College, based his 20-percent

estimate on the increase in per acre yields observed in Iowa between 1933, when only 0.7

percent of the corn acreage was hybrid, and 1943, when 99.5 percent hybrid planting was

reported and he attributed the entire advance to the use of hybrid seed [Sprague 1946:

Figure 1, p. 101].13

John Rogers, a professor of agronomy at College Station, Texas, and

Jesse Collier, at the Texas Blackman Experiment Station, simply reported without

citation ―experience in other corn-growing regions‖ [1952: 7]. None of these reports

seems a very reliable source and none explicitly examine the relative superiority of

hybrid corn in the first half of the 1930s.

The best and most appropriate data on the relative yields of different corn

varieties are the reports of field trials conducted by the agricultural experiment stations.

These remain unexploited by quantitative historians.14

Beginning with the Iowa

Agricultural Experiment Station in the early-1920s, many of the stations in corn-belt

12

There was a survey of ―scientists engaged in crop breeding‖ taken (probably) in 1938 that reported

estimates of the hybrid yield advantage that ranged from 5 to 25 percent, the authors concluded that the

probable range was 10 to 15 percent [Dowell and Jesness 1939: Table 1 and pp. 480-481]. This may have

been the source for the USDA’s 1940 report of the opinions of ―plant breeders.‖

13

The actual increase in yields between those two years was 38 percent [USDA, Track Records, 2004], but

1945 was a very poor year for Iowa corn, so perhaps Sprague, writing in 1945, tempered his estimate.

14

Although not cited in his published Econometrica article [1957b], Griliches’s unpublished Ph.D. thesis

for the University of Chicago contains a comment in an Appendix that rejects the Agricultural Experiment

Station data:

The data raise several difficult problems. They represent results on one or several fields

in the whole state, conducted under varying and better than average conditions. The

relation between the experiment station results and what the farmer may expect on his

own farm is not clear. In particular, this relation may not remain constant between

different states. For example, while the average yield in Iowa tests was around 80

bushels per acre at a time when the average yield for the state was around 40 bushels, the

North Carolina tests averaged more than 100 bushels, but at the same time the average

state yield was only around 30 bushels [Griliches, Thesis, 1957a: 56-57].

These considerations may make the Iowa test results an exaggerated estimate of the absolute advantage, but

all that is needed for Griliches’s disequilibrium model is an estimate of the relative advantage. Elsewhere

Griliches argued that the relative advantage was independent of the level of yield per acre. Moreover, to

the extent that the test results exaggerated the absolute gain, they bias the farmer’s decision calculus toward

adoption, and thus they would bias the argument against the claim I make that the hybrid advantage was not

large enough to encourage early adoptions.



states conducted controlled plantings of open-pollinated, experimental hybrid, and

commercially-available hybrid seeds and published the results in the Stations’ Bulletins.

This paper relies on the data available from the Iowa Corn Yield Tests. These are the

most complete. They begin at the earliest date. And, they are the most relevant. Iowa

was both the heart of the Corn Belt and the first state to widely and most quickly adopt

hybrid corn.

For the Iowa tests the state was partitioned into 12 districts, shown in the inset

map in Figure 7. A volunteer farmer from each district, who was also a member of the

Iowa Crop Improvement Association, planted several varieties in adjacent fields and

employed a uniform cultivation practice to raise them to maturity. At harvest, the yields

were measured separately for each variety and reported back to the Experiment Station.

The Table displayed in Figure 7 summarizes the results for the years 1926 through 1940.

For each district and each year the average yield for all hybrid varieties tested is

expressed relative to the average for all open-pollinated varieties. It is immediately clear

why the introduction of hybrid corn caused such excitement. Of the 166 observations in

the table, only two recorded a relative below 101 (district 3 in 1926 and district 8 in

1927). These data provide strong support for the concept of hybrid vigor, or ―heterosis‖

to use the scientific term. As we will see, however, hybrid vigor is not the same as

economic superiority.

Hybrid Vigor

American corn, or more properly, ―maize‖ (Zea mays, L.) is native to North America.15

It originated in Mexico where farmers cultivated it for millennia, gradually improving the

plant by the selection for genetically-based traits. Before the development of hybrid corn

15

The sources for this and the next several paragraphs are many, but the science is well-known so a

detailed list of sources will be omitted. References to the names and historical dates can be found in

Duvick [2001]. For a history of corn varieties (germplasm), see Troyer [2004]. Much of the science is

elaborated in Smith, Betrán, and Runge [2004]. A useful discussion of the relevant agricultural history is

provided by Bogue [1983].



the seed used for farm-planted corn was the result of natural cross-pollination. Under

these conditions, corn is said to be ―open-pollinated.‖ Pollen, produced by the corn

plant’s tassels, is released and carried on the air. Some of the pollen typically reaches the

cornsilks (the ―ear shoots,‖ which are the stigmas of the female flower) of one or more

nearby plants. The geminating pollen tube grows down the silk and fertilizes the egg cell,

thereby starting the growth of a seed. In principle each seed on an ear of corn could have

a different male parent. The fraction of corn seeds set by self-pollination is known to be

very low. If this fertilization process is left to the wind, selective breeding consists of

choosing individual ears of corn on the basis of desirable plant or grain properties and

saving those seeds for the following year’s crop. A great deal of natural hybridization

between separate corn populations and varieties took place in this way.16

As a

consequence of repeated selection under open-pollination, corn lines evolved that were

adapted to new climates and soil conditions such that corn cultivation spread across the

North American continent in the nineteenth century.

The next step, deliberate control of parentage, produced ―varietal hybrids‖ in

experiments conducted by farmers and agronomists in the late nineteenth and early

twentieth centuries. Ever since Charles Darwin’s experiments with inbred and cross-

pollinated corn, reported in 1876, it was known that the progeny of inbred plants were

inferior to those of the cross-bred hybrids.17

In Darwin’s terms, hybrid plants had ―innate

constitutional vigour.‖ The lack of this vigor in the inbreds is known as ―inbreeding

depression.‖ Not surprisingly, Darwin’s results stimulated experimentation with

deliberate cross-variety hybrids.

16

For a brief review of the history of maize cross pollination see Olmstead and Rhode [2008: 71-76]. The

most popular open-pollinated variety at the time that the first hybrids were introduced was Reid’s Yellow

Dent. This was an accidental hybrid between a reddish semi-gourd and a yellow flint. The story is told by

Russell Lord [1947: 147] and Troyer [2004].

17

Darwin married his first cousin and their first child was retarded. He had a life-long interest in

inbreeding.



Neither natural hybrids nor the deliberate varietal hybrids are the hybrid corn of

the hybrid revolution under discussion. Hybrid corn as it is known today is more

accurately described as a hybrid of inbred lines. Due to their inferior quality, the inbreds

were generally avoided by plant breeders. So it took a leap of imagination when George

Shull and Edward East, working independently, crossed two pure inbred lines of corn

(homozygous strains) and produced plants superior to the run-of-field open-pollinated

varieties. The results were published in 1908. The Shull-East ―single-cross‖ hybrid of

inbred lines in principle could revolutionize corn farming. Seeds could be produced on a

field-wide basis by removing the tassels from one inbred line and allowing it to be

fertilized by the pollen from a second inbred line planted in the neighboring row. It

seemed evident, however, that this approach was impractical. Producing the inbred lines

that were to be crossed involved laborious hand pollination and these parent lines were so

depressed by inbreeding that their seed yields were extremely low, making the input costs

to large-scale seed production prohibitive.

The problem of producing hybrid seed that the farmer could afford was further

compounded by the need to plant freshly-made hybrid seed each year. If the seeds of an

inbred hybrid were planted, the yields achieved the following season would drop

significantly because seed from a hybrid field would suffer from inbreeding depression

[Jugenheimer 1939: 18-19].

The practical problem was solved in 1918 by Donald F. Jones. He found that a

―double-cross‖ hybrid could be made by crossing two single-cross varieties. The

progeny, while generally not as productive as their single-cross parents, nevertheless out

performed the open-pollinated varieties. Since single crosses were prolific parents (unlike

the pure inbred lines) production costs for the double-crosses were reduced to an

economical level.

All of the hybrids in the Iowa Corn Tests recorded in the table in Figure 7 were

double-cross varieties. The trial results for the period 1926-1933 (before the drought of



1934) are plotted both as a histogram and as a density estimate in Figure 8. The average

yield advantage of the hybrids was 9.3 percent (averaging across the 12 districts and 95

observations). The median yield advantage was 9 percent. An advantage of 15 to 20

percent would be an exaggeration for this period. The average advantage in District 6,

where the adoption of hybrid corn first took place, was only 7 percent.

Although the 15-20 percent advantage cited by Griliches is an exaggeration for

the period of first adoption, perhaps the story of a disequilibrium transition would be just

as valid with the more modest 7 to 9 percentage advantage reported by the Iowa

Experiment Station. The typical yield with open-pollinated corn reported by the farmers

conducting the Iowa corn yield tests, 1926 through 1933, was 61.3 bushels per acre

[Shaw and Durost 1965, Table 12: 28]. Presumably, this represents the yield achieved

with best-practice farming by experienced farmers. The state-wide average for that

period, however, was only 38.2 bushels per acre. Thus the typical farmer could anticipate

a yield gain of less than four bushels per acre and an experienced best-practice farmer

could anticipate perhaps as much as a six-bushel gain.

Before we can conclude that an advantage in physical yield translated into an

economic advantage, we must factor in the depressed value of the corn crop and the high

price of hybrid corn seed. With the advent of the Great Depression in the 1930s, the

market price of corn came down from a high of 80 to 85 cents a bushel in the late 1920s

to 32 cents in 1931 and 1932 [Carter et al, Series Da697]. During the Depression hybrid

seed was selling in Iowa for $6.00 a bushel [Culver and Hyde 2000: 91].18

Since a bushel

of seed would plant two acres [Duvick 1992: 71], a farmer would have to expect a

financial gain approaching $3.00 an acre to be tempted to pay full price.19

Expecting no

18 Elsewhere Culver and Hyde report ―at the depths of the Depression, corn sold in Iowa for ten cents a

bushel‖ and that Pioneer’s price was $5.50 a bushel [p. 147].

19 Corn seeding rates varied widely depending upon the local practice and climate. States with abundant

rainfall, such as Ohio, supported heavier seeding rates [Fernandez-Cornejo 2004: 8].



more than 32 cents per bushel for the crop when sold, the advantage of the hybrid seed

would have had to approach nine bushels per acre, not the four to six bushels that could

be anticipated on the basis of the Iowa Corn Tests.

Henry Agard Wallace and Hybrid Hype

The puzzle then is why some adventurous farmers were willing to adopt hybrid corn

before its economic superiority was demonstrated by controlled tests. My suggestion has

two parts: (1) there was an aggressive marketing campaign launched by the commercial

seed companies directed at potential adopters, and (2) the Secretary of Agriculture, Henry

Agard Wallace, a commercial promoter of hybrid seed and former President of the major

seed company, Pioneer Hi-Bred International, put the full weight of the Federal

government behind an advocacy of hybrid corn.

Henry Agard Wallace, Franklin Roosevelt’s first Secretary of Agriculture, was a

multifaceted, complex, prolific, and eccentric man.20

He was an early champion of

scientific farming, a path-breaking plant scientist, a talented statistician and geneticist,

America’s first econometrician, author of a dozen books, a journalist, and the influential

editor of Wallaces’ Farmer, from 1921 to 1933, the most prominent agricultural

magazine of its time.21

Later he became the editor of The New Republic, 1946-1948.

Wallace was a successful entrepreneur who made a personal fortune as the leading

founder of the Hi-Bred Seed Company (later Pioneer Hi-Bred International, Inc.). Today,

Pioneer is a wholly-owned subsidiary of E.I. du Pont de Nemours and Company and is

the largest seed company in the world with a market share in 1997 of 42 percent

[Fernandez-Cornejo 2004: Table 12, p. 26; Beck 2004: 568]. Henry Agard Wallace was,

20

As one index of his eccentricity, I note that Wallace was a mystic and an ambidextrous, vegetarian,

teetotaler before any of these affectations was considered legitimate. Republican teetotalers holding high

office in Roosevelt’s New Deal administration were rare indeed. The best biography of Wallace is by John

C. Culver and John Hyde [2000] from which I draw the details in this paragraph.

21

It was the USDA’s statistician Louis Bean that named Henry A. Wallace the first American

econometrician based on Wallace’s book, Agricultural Prices [1920]. See Culver and Hyde [2000: 51].



according to historian Arthur Schlesinger Jr [2000], America’s best Secretary of

Agriculture.22

He was Vice President of the United States during World War II – the

most influential and powerful Vice President before Dick Cheney. Wallace served as

Secretary of Commerce during the economic transition to peace time (1945-1946). He

ran for President on the Progressive Party ticket in 1948. The Des Moines Register

identified Henry A. Wallace the "Most Influential Iowan of the 20th Century" on

December 31, 1999. His biographers identified him as the ―state’s greatest son‖ [Culver

and Hyde 2000: ix]. When he died of Lou Gehrig’s disease in 1965, the then-reigning

Secretary of Agriculture, Orville Freeman, could declare, without hyperbole that: ―No

individual has contributed more to the abundance we enjoy today than Henry Wallace‖

[p. 531].

A unifying theme – an obsession, really – for Wallace throughout this prolific and

many-sided career was hybrid corn. In 1910, two years after Shull and East reported on

their single-cross inbred hybrid experiments, Wallace was debating the findings with

Iowa State College agronomists in Ames. In 1912 he conducted his own experiments to

produce single-cross hybrids. At the time, he concluded that the difficulty of hand

pollination ―was too laborious‖ [Wallace quoted by Culver and Hyde 2000: 67]. Over

the next several years Wallace experimented with varietal hybrids without achieving

consistent success. But when Edward East visited Wallace in 1919 and introduced him to

Donald Jones’ results with double-cross hybrids, Wallace immediately saw the

commercial potential and began his own experiments with the new technique. He also

used the pages of Wallaces’ Farmer to proclaim the coming revolution [Culver and Hyde

2000: 68]. In 1920 the circulation of Wallaces’ Farmer was 65,200 [Galambos 1968:

344]. The journal was read by a high proportion of corn and hog farmers.

22

Precision requires that I use Wallace’s middle name since his father, Henry Cantwell Wallace, was also

Secretary of Agriculture (1921-1924), appointed by Warren Harding. Another Henry Wallace in the family

was Henry A. Wallace’s grandfather and the founder of Wallaces’ Farmer. This Wallace had no middle

name [Lord 1947].



In 1920 Wallace convinced the Iowa State Agronomist, H.D. Hughes, to establish

the Iowa Corn Yield Tests. The idea was to challenge the current practice of judging

corn by the physical appearance of the ear and instead focus on yields per acre. Wallace

did not have enough seed to offer an entry of his own that first year, and his entry for

1921 failed to outperform the best of the open-pollinated varieties. He entered a new

hybrid, named Copper Cross, in the 1922 tests and again in 1923, but it too failed to out-

yield the best open-pollinated entries. However, Copper Cross was successful enough

that Wallace was able to draw up a contract for its commercial release with the Iowa Seed

Company. When Copper Cross won the gold medal at the 1924 test, the

commercialization of hybrid corn was launched.23

Wallace himself wrote the first

advertising copy. ―An Astonishing Product—Produces Astonishing Results … If you try

it this year you will be among the first to experiment with this new departure, which will

eventually increase corn production of the U.S. by millions of bushels‖ [quoted by Culver

and Hyde 2000: 71].

In 1926 Wallace founded the Hi-Bred Seed Company [Culver and Hyde 2000: 82-

83]. He continued to use the pages of Wallaces’ Farmer to proclaim the virtues of hybrid

corn and, of course, to advertise his company’s seed. In that same year and the following

year hybrid maize did reasonably well in the Iowa Corn Yield Tests recording about a 7

percent greater yield than their open-pollinated rivals. But that was an insufficient

advantage to create much demand.

There were several obstacles, not the least of which was the astonishing price that

Wallace was asking for his ―astonishing‖ seed – it was $52 bushel in 1924 [May 1949:

514, Culver and Hyde 2000: 71]. Two founding principles of the Hi-Bred Seed Company

were first, total honesty in advertising and, second, high prices. ―High prices, Wallace

believed, were necessary to convince farmers they were buying something special‖ and,

23

The Funk Brothers Seed Company introduced its first double-cross hybrid in 1928 [Fitzgerald 1990:

218].



of course, high profits helped cover the cost of on-going research intended to improve the

varieties [Culver and Hyde 2000: 91 and 148].

Another obstacle that had to be overcome was the reluctance of many farmers to

abandon their reliance on their own home-grown seed and instead entertain a visit by, and

the commercial pitch of, the traveling seed salesman. The role of the salesman was not

so much to educate the farmer – the genetics of inbred-hybrid crosses and the ―magic‖ of

heterosis exceeded the common-sense knowledge of most farmers and indeed of most

seed salesman. The claims of superiority had to be accepted, if they were, on faith. It was

a particularly sore point with many farmers that seeds saved from a hybrid crop could not

themselves be planted the next season with any hope of success. So, old habits were

challenged. A commitment to hybrid seed was tantamount to an agreement to deal with

the seed salesman every subsequent year as well as the current year. And that

commitment meant that the farmer’s skill in selecting seed corn from his own crop, a skill

which many took great pride in, would be no longer needed or esteemed [Fitzgerald

1993].

Pioneer Hi-Bred designed a sophisticated marketing plan to address these

problems. Seed salesmen working for Wallace offered to provide the reluctant farmer

enough seed free of charge to plant half of his acreage. The farmer would plant the

remaining land with the open-pollinated seed he preferred. In exchange the Hi-Bred

company would reclaim one-half of the increased crop produced by its seed judged

against the farmer’s regular crop [Lee 1984: 43, Culver and Hyde 2000: 91]. Typically,

only one farmer on each lane was offered the deal with the hope that a demonstration

would spread interest to the neighborhood. Other farmers were given yield guarantees

[May 1949: 514]. According to Culver and Hyde, it often took several years to persuade

a farmer that the higher yields achieved with the Hi-Bred seed were not a fluke [p. 91].

With the advent of the Great Depression in the 1930s, marketing the new seed

became even more difficult. As I have noted, the Depression had sent the market price of



corn tumbling from a high of 85 cents a bushel in the late 1920s to 32 cents in 1932 and

Iowa farmers, many who faced ruin, were hardly in the mood for experimentation and

risk taking. Safety first was the general rule. Moreover the average yield gains from

switching to hybrids were, as I have already pointed out, generally insufficient to justify

the cost of seed.

Henry Agard Wallace became President Roosevelt’s Secretary of Agriculture in

1933. The public position did not damp his enthusiasm for hybrid corn. For many years

the Agriculture Department had published an annual volume, The Yearbook of

Agriculture, devoted to reporting on the activities of the Department, of advances in

many fields, and offering both general and specific advice to farmers. The Yearbooks

had large press runs and were widely distributed by members of Congress to their

farming constituency. For the 1936 edition Wallace made an unusual decision. As he

explained:

The 1936 Yearbook of Agriculture differs … from those published in

recent years. … This year it is devoted to a single subject – the creative

development of new forms of life through plant and animal breeding

[Wallace 1936: foreword].

The article on ―Corn Improvement‖ for this Yearbook was written by Merle T. Jenkins,

the USDA’s Principal Agronomist. A headline exaggeratedly claimed ―Yield Advances

up to 35 Percent over Open-Pollinated Varieties‖ [Jenkins 1936: 481]. The report was

based on the Iowa Corn Yield Test despite the exaggeration of the headline.

In retrospect, and perhaps even at the time, the focus of the 1936 Yearbook was in

jarring contrast to other efforts of the Roosevelt Administration to deal with the Great

Depression. For the first several years of his administration, Wallace presided over the

acreage reduction and crop destruction policies of the Agricultural Adjustment

Administration. He was the one who ordered the plowing up of ten million acres of

cotton in 1933 and the slaughter of six million baby pigs and sows in September [Culver



and Hyde 2000: 123-125]. Yet Wallace looked into the future beyond the current crisis

to foresee a time when the yield increases to be made possible by the spread of hybrid

corn would be welcome.

By today’s standards, the glaring conflict of interest between Wallace’s financial

interest in the Pioneer Hi-Bred Company and the use of the government agency he

controlled to advertise and advocate his product would be outrageous. But even this

propaganda barrage combined with the innovative marketing strategy of his company

might not have been successful in tipping the balance in favor of hybrid corn. It took two

other factors to put the company on the road to success.

Drought and Research

The eventual success of hybrid corn was due, first, to a tipping event and then to the self-

reinforcing momentum of biotechnology. The factor which acted to tip the balance in

favor of hybrid adoption was paradoxically another disaster to bedevil corn farmers in the

1930s. As if the Depression, with its devastating impact on agricultural prices were not

enough, there were catastrophic droughts in 1934 and 1936. An index of the severity of

these droughts, as we have suggested, is the fraction of the crop planted which was

harvested. In Iowa and in the country overall, thirty to forty percent of the acreage

planted was so devastated by drought that it was not worth harvesting. In Nebraska and

Kansas the losses were nearly total. Consult Figures 2 and 3.

What the droughts starkly demonstrated was that the relative yield of hybrid corn

was greatest when the absolute yields were generally depressed. Figure 9 reveals the

relationship using, once again, the Iowa Corn Yield Test results to illustrate the

correlation. In the extreme drought conditions of the mid 1930s, the yield differences

between the new and traditional varieties were stark. Edward May, President of the May

Seed Company, recalled:



Yield differences became plainly evident in 1936, which was also a

severe drouth year in Iowa. At this time nearly all farmers who were

testing hybrid seed corn planted only a limited acreage. Yields of

hybrids under these conditions in many areas of the state were

approximately double the yields of other corn grown on the farm. The

results were so convincing that it marked the end of the vast efforts of

initial adoption [May 1949: 514].

―Almost overnight, demand for hybrid seed exploded‖ [Culver and Hyde 2000: 149].

Big percentage point gains in adoption came in 1937: 22.3 percentage points accounted

for by new adoptions in Illinois, 21.2 percentage points Iowa, 18.3 points in Ohio, 17.4 in

Indiana, 12.9 in Wisconsin [see footnote 3 for sources].

Once the move to hybrid corn was launched -- and only because the switch was

made – the technological diffusion process became self-sustaining and irreversible. The

steady improvement of the yield advantage of hybrid corn began in 1937. See Figure 6,

but also Figure 10 which illustrates the shift in the relative hybrid advantage after 1936.

Farmers might have switched to hybrid corn out of fear of continued drought, but soon

the genetic advance in hybrid corn made open-pollinated corn obsolete even though the

price of hybrid seed was high and a farmer using it would need to purchase fresh seed

each season. This genetic improvement was achieved thanks to continuing research

funded by the seed companies using retained earnings generated by soaring sales and

high prices.

Wallace believed that his hybrid revolution would have collapsed without a

continuing, well-financed, research effort [Culver and Hyde 2000: 148]. Research by the

federal government also played a supporting role.24

The research in both sectors was

closely co-coordinated. According to Sprague [1946: 101] there was unrestricted

24

In 1922 when Henry Agard Wallace’s father, Henry C. Wallace, was Secretary of Agriculture a well-

funded hybrid corn research program was established by the Department in cooperation with the

Experiment Stations in several corn-belt states. This federal program was vital during the 1920s. Donald

Duvick suggests that ―the commercial maize breeders probably could not have succeeded in the early years

[without the contributions from the public sector], for individually they simply did not have enough inbred

lines …‖ [Duvick 2001: 71].



interchange of ideas and seed stock between government researchers and the private

companies. Most observers agree that the for-profit research was the driving partner of

the private-federal joint effort after 1937 [Griliches 1958: 420-421 and Table 1, p. 424;

Duvick 2001: 71; Fuglie, Ballenger, et al 1996: 45, Fernandez-Cornejo 2004: 41-50].

Wallace claimed that his company spent more money on corn research than the USDA

and the state experiment stations combined [Culver and Hyde 2000: 148].

Ironically, the drought of 1934 was, in part, responsible for the remarkable

improvement in hybrid development seen thereafter. One of the farmers that Hi-Bred

recruited as part of its experimental research on new hybrid strains suffered greatly in the

drought of 1934. Most of his experimental plants were lost. But he continued to work

with the few plants that had managed to survive. The result was the unexpected

discovery of a hardy new hybrid, number 307, with a remarkable ability to withstand

drought. Consult Figure 6 again, where number 307 is labeled for easy identification.

The experimenter remarked that this plant ―proved very valuable when we found

ourselves in another serious drought condition in the summer of 1936‖ [Culver and Hyde

2000: 149].

What we have, then, is a story of the diffusion of hybrid corn that is more

complex and more interesting than the one usually told by Griliches-inspired plant

scientists [Griliches, Science, 1960]. Rather than disequilibrium transition slowed by

information imperfections that were gradually overcome by commercial advertising and

agricultural extension education, the history reveals that neither the innovation of 1918,

nor the commercial product of 1924, nor the highly-touted seeds of 1936 were

economically and culturally attractive. The advertising and marketing campaigns of the

seed companies were effective in the late 1920s or early 1930s not because they educated

farmers, but because they offered inducements designed to lower the costs and risks of

adoption, shifting those costs and risks to the seed companies. The tipping point came in

1936 when farmers choose what seeds to plant in 1937. How much credit should be



given to the Yearbook of Agriculture that year and how much to the drought would be

difficult to say given their simultaneity. But what is clear is that the genetic advance in

hybrid corn varieties beginning with hybrid 307 (which was introduced commercially in

1936) is what locked in the transitional adopters and made the hybrid revolution seem

inevitable in retrospect. Had Wallace not used the bully pulpit of the USDA to promote

his own commercial and financial interests, had the USDA not supported the research

effort in the late 1920s and early 1930s, had the droughts of 1934 and 1936 not occurred,

had Hi-Bred not continued a major research effort following 1936, the Wallace crusade

might have succumbed as just another fatality of the Great Depression.

The Impact of the Drought on Adoption: An Illustration

The relationship between the drought and the adoption of hybrid corn can be illustrated

using crop district data for the years 1926-1960. For the purposes of reporting the data

on the percentage of acreage planted to hybrid varieties and the statistics of acreage and

output, the USDA partitioned each of the corn states into nine (or fewer) districts that

aggregated contiguous counties. Unfortunately the county-level data on acreage planted

is not complete and the data on yields is available only for Ohio, Indiana, Illinois,

Wisconsin, Iowa, Missouri, eastern South Dakota, and eastern Nebraska. Michigan and

Kansas are not yet available. Because the data on acreage planted is not available at the

county or district level for most of these states, I use the yield per harvested acre as my

measure of the severity of the drought in 1936. Specifically severity is measured as the

percentage yield shortfall in 1936 when compared to the average yield for 1926-1935

excluding 1934.

The more severe the 1936 drought, the greater its depressing impact within a crop

district, the faster we expect the adoption of the new drought-resistant hybrids would

have been. Zvi Griliches collected annual data on the percentage of acreage planted in

each crop district that was devoted to hybrid varieties. District-by-district he fit a simple

three-parameter logistic curve to estimate the timing and speed of adoption. We used the



parameters that he published [Griliches 1957, Table 2] to calculate three measures:25

(1)

the year that the district achieved a 40-percent adoption rate, (2) the number of years that

elapsed between the time a 10-percent adoption rate was achieved and a 70-percent

adoption rate was recorded, and (3) the percentage of new acreage adopting hybrid corn

in 1937 compared with 1936. I name these three variables: ―penetration,‖

―cautiousness,‖ and ―jump.‖

We also conjecture that the eagerness to adopt the new varieties would be

correlated with the productivity of corn farming within the district. The higher the yield

per acre in normal years, the larger will be the pecuniary advantage of the higher yields

the new varieties seemed to offer.

Penetration: A 40-percent rate of adoption would indicate that hybrid corn had

made significant inroads in the region. Penetration is the date (in years) this threshold

was achieved. The average over the 44 crop districts was 1939. The smaller this

number, the earlier substantial penetration was achieved. I performed a simple statistical

calculation to predict the year that 40-percent penetration was achieved for a cross

section of the 44 crop reporting districts in the cotton belt. See the map inset in Figure

11. The average yield reported for the 1926-1933 and 1935 period and our measure of

the yield shortfall in 1936 were used as linear regressors. The larger the shortfall in yield,

the greater severity of the drought, and thus the earlier penetration should have been

achieved. The regression confirms this relationship. The higher the normal yield per

acre the earlier 40-percent penetration was achieved. Both coefficients are statistically

significant at the 96 percent level. The regression statistics are presented in Figure 11.

25

A purest might prefer to use the original data rather than the fitted curves. I have been unable to locate

the original data. However, the fit of each curve as reported by Griliches is very high. Moreover, there is

certain logic in using the fitted values since they create a continuous variable, smooth the data, and correct

for noise in the original crop reporters’ estimates.



Cautiousness: I expect that a severe drought would reduce caution and

accelerate the speed of adoption. The results, also in Figure 11, confirm this conjecture.

The larger the shortfall in the 1936 crop the faster the diffusion process proceeded.

Jump: The size of the jump in adoption rates, measured between 1936 and 1937,

would be expected to be positively related to yield and to the shortfall. These results are

also presented in Table 11. Both coefficients have the predicted sign. Large yields and

large losses in 1936 are associated with a bigger jump between 1936 and 1937.

We conclude that the drought of 1936 sped the process of adoption after it

revealed the drought resistance of hybrid corn. The commercial seed producers were

quick to spread the word. An advertisement for DeKalb seed published in the Prairie

Farmer of October 24, 1936 prominently featured hybrid corn’s drought resistance and

claimed it had been proven in eight corn belt states from Nebraska to Ohio [reproduced in

Fitzgerald 1990: 176]. After 1937 a new dynamic was set in motion. The explosion of

demand for hybrid corn generated large profits for the major hybrid seed companies:

Pioneer, Funk, and DeKalb. As a result prices of hybrid seed fell and the companies

invested heavily in research with new hybrid strains. They not only perfected the drought

resistance of the plant, but found ways to permit increased planning density, increase the

resistance to lodging, and increase responsiveness to artificial fertilizer. The result was a

steady improvement in the yields per acre that hybrid corn could achieve. Once these

post-1937 improvements were recognized adoption of hybrid corn became economically

advantageous; before 1937 it had not been so.

We can trace the diffusion of hybrid corn from district to district. The insert map

in Figure 11 illustrates when the various districts achieved 40-percent penetration. The

crop district in the center of the Corn Belt (Iowa District 6) was the epicenter for the

spread of the innovation. It had reached 40 percent in 1936. Eleven districts, all located

in a concentric ring around the origin districts achieved that threshold in 1937 in the rush

to achieve some protection in case another dry year were to follow. In 1938 the



concentric ring expanded to the north and west. In 1938 there were also four districts in

northern Indiana and northwest Ohio that reached the penetration threshold. These

districts were less affected by the drought of 1936. It is possible that a geographical

contagion coupled with new and superior varieties introduced for the 1938 crop year

explain this move into northern and central Indiana and Ohio. Central Indiana and Ohio

filled in the map in 1939. The southern tier of those states did not reach 40 percent until

1940 or after.

The sociologists Bryce Ryan and Neal Gross, writing in 1950, studied the

diffusion of hybrid corn in two communities located in Greene County, Iowa [Ryan and

Gross 1950]. In their view late adopters were farmers bound by tradition. They were

irrational, backward, and ―rural.‖ The early adopters by contrast were flexible,

calculating, receptive, and ―urbanized.‖ ―Certainly,‖ they summarized, ―farmers refusing

to accept hybrid corn even for trial until after 1937 or 1938 were conservative beyond all

demands of reasonable business methods‖ [p. 672]. They drew a policy implication.

―The interest of a technically progressive agriculture may not be well served by social

policies designed to preserve or revivify the traditional rural-folk community‖ [p. 708].

In part this view was based on Ryan and Gross’ (incorrect) belief that hybrid corn was

profitable in the early 1930s [p. 668]. I have suggested that this was not the case. The

map in Figure 11 should also give pause to the view that rural laggards delayed the

adoption of hybrid corn. It would be hard to argue that the farmers in Iowa Crop

Reporting District 6 were predominantly forward-thinking leaders, attentive, and flexible,

while those in Indiana and Ohio were predominately backward rustics trapped by

inflexible folk tradition.

I think an implication of this study is that farmers (even those of rural America in

the 1930s) are remarkably resilient and adaptive. Sudden and dramatic climate change

induced a prompt and prudent response. An unexpected consequence was that an

otherwise more gradual process of technological development and adoption was given a



kick start by the drought and the farmers’ response. That pushed the technology beyond

a tipping point and propelled the major Corn Belt states to the universal adoption of

hybrid corn by 1943. The country as a whole reached universal adoption by 1960.

While this process was driven by individual farmers and privately-owned seed

companies, there was also a role played by the government. The USDA not only

campaigned vigorously for hybrid corn from 1936 onward, but engaged in the years

before 1936 in its own research, and subsidized the dissemination of knowledge and seed

samples. That this engagement was to some extent promoted by the Secretary of

Agriculture, Henry Agard Wallace, a hybrid researcher and the founder of the major

commercial producer of hybrid seed, should not blind us from recognizing the

importance of the government subsidizes in preparing the new technology for the leap

forward.



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Zuber, Marcus S., and Joe L. Robinson. 1941. "The 1940 Iowa Corn Yield Test," [Iowa]

Agricultural Experiment Station Bulletin P19(NS) February 1941: 519-593.



Based on Schubert, Suarez, et al [2004] Figure 1, p. 1855.

1932-1938 Composite

Precipitation Anomaly

Based on the 1950 Census of Agriculture. Counties with 25

percent or more of acreage planted to corn.

The American Corn Belt

Figure 1



Figure 2

1925 1930 1935 1940 1945 1950

10

20

30

40

50

60

70

80

90

100

Percent of Acreage Plantedthat was Havested

Yield in Bushelsper Acre Harvested

Iowa

1934

1936



Figure 3

1925 1930 1935 1940 1945 1950

10

20

30

40

50

60

70

80

90

100



Illinois

19341936

1925 1930 1935 1940 1945 1950

0

10

20

30

40

50

60

70

80

90

100



Kansas

1934 1936



1932 1934 1936 1938 1940 1942 1944 1946 1948 1950 1952 1954 1956 1958 1960

0

20

40

60

80

100

Percent of Corn Acreage Planted

to Hybrid Varieties

96.3%

Source: Acreage planted to hybrid seed corn from USDA, Agricultural Statistics, 1962, Table 46, p. 41, divided by acreage planted to corn from

USDA, National Agricultural Statistics Service, Historical Track Records, April 2004, p.19.

1932 1934 1936 1938 1940 1942 1944 1946 1948 1950 1952 1954 1956 1958 1960

0

20000

40000

60000

80000

100000

120000

Acres Planted to Corn

Total

Hybrid

Figure 4



1875 1900 1925 1950 1975 2000

0

40

80

120

160

U.S. Corn Yields, 1866-2002

Bushels per

Acre

Source: Carter, et al. 2006: Series Da693-694. USDA, National Agricultural Statistics Service, 2004: 7 & 9.

Open-pollinated corn

Increasing

adoption of

double-cross

hybrid corn

1%

96%

single-cross

hybrid corn

99%

Figure 5



Figure 6

β = 1.16 bushels/year

RYD = Reid’s Yellow Dent (open pollinated)

Average over three planting densities

[12K, 19K, 26K plants per acre]

Hybrid 307

RYD

50

70

90

110

130

150

Bushels

per

Acre

1920 1940 1960 1980 2000Year of Introduction

Hybrid Grain Yield by Year of

Introduction of the Variety

Source: Dan N. Duvick, “Genetic Contributions to Advances in Yield of U.S. Maize,” Maydica (37) 1992: 69-79; Table 3, p. 73.

β = 1.16 bushels/year

RYD = Reid’s Yellow Dent (open pollinated)

Average over three planting densities

[12K, 19K, 26K plants per acre]

Hybrid 307



District 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940

1 117 109 110 109 114 116 115 114 112 111 107 107 115 110 108

2 105 117 120 124 113 * 102 110 101 109 118 109 109 115 122

3 97 103 109 114 111 106 102 107 119 106 126 112 118 114 +

4 116 105 110 110 116 112 107 129 111 121 * 108 114 113 121

5 107 111 108 108 114 113 108 128 108 107 129 114 112 107 127

6 105 110 103 103 105 109 106 116 106 103 117 108 117 116 115

7 105 103 114 109 113 107 112 * 150 131 120 121

10 111 102 111 108 102 105 102 140 133 120 141 132

8 104 98 115 109 124 108 110 127 109 112 112 116

11 103 114 108 112 111 106 111 154 114 134 115 #

9 105 102 114 114 106 107 106 149 114 106 110 122

12 110 107 104 106 103 102 100 141 118 115 108 118

* Crop lost -- drought

+ Poor crop -- "not calculated"

# Crop abandoned -- wire worms

105 115 105

*109 122

114 149 113

Iowa Corn Yield Tests, 1926-1940

Relative Average Yield for all Hybrid Varieties

All Open-Pollinated Varieties = 100

Note: For 1933-1935 districts 10, 11, and 12 were

combined with districts 7, 8, and 9 respectively.

Source: Marcus S. Zuber and Joe L. Robinson, “The 1940 Iowa Corn Yield Test,”

[Iowa] Agricultural Experiment Station Bulletin P19 NS, February 1941:589.

Figure 7



0.0

2.0

4.0

6.0

8

90 100 110 120 130

Density Estimate of Relative Hybrid Yield

1926-1933 Iowa Corn Yield Tests

12 districts

N = 95

median 109

mean 109.3

std dev = 5.9

Relative Yield

[open-pollinated varieties = 100]

MIN = 97 MAX = 129

Figure 8



Figure 9

0 20 40 60 80 100

100

110

120

130

140

150

160

Average Yield of Open- Pollinated Corn

Bushels per Acre

Relat ive Yield

of Hybrid Corn

[open-

pollinated

variet ies =

100]

Relat ive Advantage of

Hybrid Variet ies Best When

Yields are Depressed by

Unfavorable Weather

1935- 1938

n = 43



0.0

2.0

4.0

6.0

8

100 120 140 160

1926-1933

median 109

mean 109.8

std dev = 5.9

1937-1939

median 114

mean 116.1

std dev = 9.9

Relative Yield

[open-pollinated varieties = 100]

Figure 10



Regression Estimates of the Reaction to the Severity of the 1936 Drought

44 Crop Districts in the Corn Belt

Dependent Variable

Penetration

Cautiousness

Jump

Independent Variables:

Yield

-0.257

-0.068

1.067

Shortfall

-0.015

-0.011

0.074

Constant 1948.2 6.02 -30.17

R-squared

0.668

0.125

0.464

Mean of Dependent Variable

1938.89

3.272

9.145

Standard Error of Dependent Variable 0.23 0.138 1.143

Figure 11

Insufficient data

Not in Corn Belt

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